The invention relates to the field of intraluminal catheters, and particularly to guiding or angiography catheters suitable for intravascular procedures such as angioplasty and/or stent deployment, and the like.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a shaped distal section is percutaneously introduced into the patient""s vasculature by a conventional xe2x80x9cSeldingerxe2x80x9d technique and then advanced through the patient""s vasculature until the shaped distal section of the guiding catheter is adjacent to the ostium of a desired coronary artery. The proximal end of the guiding catheter, which extends out of the patient, is torqued to rotate the shaped distal section. As the distal section rotates, it is guided into desired coronary ostium. The distal section of the guiding catheter is shaped so as to engage a surface of the ascending aorta and thereby seat the distal end of the guiding catheter in the desired coronary ostium and to hold the catheter in that position during the procedures when other intravascular devices such a guidewires and balloon catheters are being advanced through the inner lumen of the guiding catheter.
In the typical PTCA or stent delivery procedures, the balloon catheter with a guidewire disposed within an inner lumen of the balloon catheter is advanced within the inner lumen of the guiding catheter which has been appropriately positioned with its distal tip seated within the desired coronary ostium. The guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated or a location where a stent is to be deployed. A balloon catheter is advanced into the patient""s coronary anatomy over the previously introduced guidewire until the balloon on the distal portion of the balloon catheter is properly positioned across the lesion. Once properly positioned, the balloon is inflated with inflation fluid one or more times to a predetermined size so that in the case of the PTCA procedure, the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. In the case of stent deployment, the balloon is inflated to plastically expand the stent within the stenotic region. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation or stent deployment but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom.
Generally, the stent deployment occurs after a PTCA procedure has been performed at the stenotic site. However, recently, in some situations the stent deployment and lesion dilatation is accomplished simultaneously. In addition to their use in PTCA and stent delivery procedures, guiding catheters are used to advance a variety of electrophysiology catheters and other therapeutic and diagnostic devices into the coronary arteries, the coronary sinus, the heart chambers, neurological and other intracorporeal locations for sensing, pacing, ablation and other procedures. For example, one particularly attractive procedure for treating patients with congestive heart failure (CHF) involves introduction of a pacing lead into the patient""s coronary sinus and advancing the lead until the distal end thereof is disposed within the patient""s great coronary vein which extends from the end of the coronary sinus. A second pacing lead is disposed within the patient""s right ventricle and both the left and right ventricle are paced, resulting in greater pumping efficiencies and blood flow out of the heart which minimizes the effects of CHF. Current construction of many commercially available guiding catheters include an elongated shaft of a polymeric tubular member with reinforcing strands (usually metallic or high strength polymers) within the wall of the tubular member. The strands are usually braided into a reinforcing structure. The strands are for the most part unrestrained except by the polymeric wall. The desired shape in the distal section of the catheter, which facilitates its deployment at the desired intracorporeal location, is typically formed by shaping the distal section into the desired shape and heat setting the polymeric material of the catheter wall to maintain the desired shape. There is usually some spring-back after the heat formation due to the reinforcing braid, but this is usually compensated for in the shape the catheter is held in during the heat setting.
Clinical requirements from utilization of guiding catheters to advance electrophysiology catheters and the like have resulted in an increase in the transverse dimensions of the inner lumens of guiding catheters to accommodate a greater variety of intracorporeal devices and a decrease in the outer transverse dimensions of the guiding catheter to present a lower profile and thereby facilitate advancement within the patient""s body lumens and openings.
What has been needed is a catheter design which would allow for continued thinning of the catheter wall while facilitating the formation of the shape of the distal end of the catheter.
The present invention is directed to an improved catheter shaft construction which can be employed in guiding or angiography catheters for angioplasty procedures.
The catheter shaft of the invention generally includes an elongated tubular member having an inner lumen extending therein. The catheter shaft has a wall construction, which comprises a combination of multiple, preferably two layers of wire, cord or fiber reinforcement. One of them consists of a left hand and right hand set of wires wound at a lay angle of about xc2x120xc2x0 to about xc2x175xc2x0, preferably about xc2x140xc2x0 to about xc2x170xc2x0, most preferably about xc2x165xc2x0, with respect to the longitudinal axis of the tubular shaft, and the other layer of wire is wound in a substantially circumferential manner (coiled) at a preferred pitch of approximately twice the wire width along the same longitudinal axis. The circumferential coil has such a pitch as to yield a percent coverage of between about 10% and about 80%, preferably about 50%. The combination of the two layers, along with the properties of the polymer matrix used, provides the catheter shaft the desired structural properties, such as, torsional stiffness, torsional collapse load, bending stiffness, and bend kink. The structural properties of this wall construction can also be easily modified by varying one or more of the design parameters, such as wire material, wire size, wire volume fraction, braid lay angle, coil pitch or matrix polymer.
The expression xe2x80x9coblique wound layerxe2x80x9d is used in the text of this application for one of the two layers of the wall construction and it represents the layer of wire braided at a lay angle of from about xc2x120xc2x0 to about xc2x175xc2x0, preferably about xc2x140xc2x0 to about xc2x170xc2x0, most preferably about xc2x165xc2x0, with respect to the longitudinal axis of the tubular shaft.
The expression xe2x80x9ccircumferential wound layerxe2x80x9d in general refers to a coil of pitch about twice the wire width, yielding a coil coverage of about 50%. The coil coverage is defined as the ratio of wire width to pitch expressed as a percentage. This pitch may be varied to provide from about 10% coverage to about 80% coverage to accommodate the structural needs.
The wires suitable for the present invention include any stiff filamentary fibers, such as, but not limited to, carbon or boron fiber, glass, ceramic or graphite non-metallic wires, Kevlar (polyaramid), metallic wires such as stainless steel ribbons or a superelastic metal such as Nitinol, natural and synthetic fibers such as nylon, and polyesters fibers. The wire reinforcement of the oblique wound layer can be braided or filament wound. If braided, a triaxial braid may be used incorporating longitudinal fibers of the same or different fiber material.
The two layers of wire reinforcement are surrounded and stabilized by a polymer matrix which is formed of any polymer or elastomeric compound such as, but not limited to, nylons, polyurethanes, polyesters, polyimides, rubbers, silicone, PEEK or polytetrafluoroethylene (PTFE or Teflon). The polymeric material may be applied to the wires before or after they are braided/wounded to a tubular structure. The impregnation of the stabilizing matrix can be carried out by a variety of known processes, such as extrusion, pultrusion, molding or shrink tubing.
The two wire layers can be formed in either order; the substantially circumferential wound layer innermost or the oblique wound layer innermost. If the substantially circumferential wound layer composed of preferably round wire is the innermost wire layer and the oblique wound layer is the outer layer to the innermost wire layer, a closely wound inner wire would form a relatively smooth inner surface of the catheter shaft without the need of an additional inner polymeric liner. However, a lubricious coating may be added to the inner wire surface if required.
Alternatively, the oblique wound layer can be the innermost wire layer, and the substantially circumferential wound layer is the outer layer to the innermost wire layer. In this construction, the stabilizing polymer matrix surrounding the innermost oblique wound layer may also form a smooth inner surface. A lubricious coating may be optionally added to the inner surface.
As a presently preferred embodiment of the invention, a guiding catheter comprises an elongated shaft having an inner lumen extending therein. The catheter has the dual layer wire reinforced wall construction as described above. The distal portion of the catheter is given a shape (e.g., Judkins or Amplatz shapes) to facilitate the advancement and seating thereof within a desired coronary ostium and the distal tip is provided with a soft tip construction, such as described in U.S. Pat. No. 5,234,416 which is incorporated herein by reference.
The present invention not only offers reduction in wall thickness, thereby allowing larger lumens, but also provides the guiding catheter a significant increase in torque transmission and collapse performance. Furthermore, the dual layer wall construction of the present invention allows a greater degree of design freedom to meet the structural objectives. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.